In OFDM (Orthogonal Frequency-Division Multiplexing) wireless communication, transmission quality is degraded by fading in a channel. A degree of degradation of the transmission quality is not constant but varies due to noise, interference wave, or the like. Thus, adaptive modulation is performed which involves changing a modulation type for primary modulation, and error correction type and the like according to a channel characteristic indicative of distortion of a phase and an amplitude occurring in a channel between a transmitter and a receiver, as in, for example, an adaptive-modulation controller disclosed in Unexamined Japanese Patent Application Kokai Publication No. 2011-72024. For example, the controller executes adaptive modulation as follows. Upon determining that the phase and the amplitude are not substantially distorted and the channel characteristic is appropriate, the controller prioritizes transmission efficiency and uses 16QAM (Quadrature Amplitude Modulation) as a modulation type for primary modulation. Upon determining that the channel characteristic is degraded, the controller prioritizes improvement of BER (Bit Error Rate) and uses QPSK (Quadrature Phase Shift Keying) as a modulation type.